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In recent years, there has been a dramatic rise in our understanding of contact dermatitis. This paper is a review of our knowledge of the mechanisms involved in contact dermatitis and related phenomena, the investigation of these events and the emergence of significant new allergens during the last 5 years. [ABSTRACT FROM AUTHOR]

A molecular analysis of cross-reactions in costus-sensitive patients reveals that the most active sesquiterpene lactones are the ones with the lesser number of oxygenated substituents close to the a-methylene-y-butyrolactone ring. Cross-reactions with sesquiterpene lactones with different skeletons (germacranolide and guaianolide or pseudoguianolide lactones) can probably be explained by concomitant multiple sensitization to two lactones present in costus, respectively costunolide and dehydrocostus lactone. [ABSTRACT FROM AUTHOR]

Allergic contact dermatitis is essentially enantiospecific sensitization to one enantiomer generally does not imply elicitation to the mirror-image allergens. Examples from patients allergic to Frullania, and from the literature (usnic acids, 4-methoxy-dalbergiones, γ-methyl-α-methylene-γbutyrolactones, frullanolides) are discussed. [ABSTRACT FROM AUTHOR]

This article discusses true cross-sensitization and false cross-sensitization which occurs when two mixtures, for instance, contain the same allergen or when cross-reaction cannot be rationalized, or polysensitization. Cross-reaction is observed when a subject, initially sensitized to an allergen reacts to a second allergen with which he has not been in contact previously. The first compound is the primary sensitizer while the second is a secondary sensitizer. In man it is rarely possible to know for certain the actual primary sensitizer, as he may have been exposed earlier to thousands of compounds including the one to which he cross-reacts. Cross-sensitization is often used by dermatologists to imply a simultaneous reaction to two or more products. Whenever allergic contact dermititis is concerned cross-sensitivity is used. Guinea pig and mouse, combined with an informed and careful dermatological chemist, offer the greatest opportunities for expanding knowledge of structure-function in cross-sensitization.

The sensitizing capacities of helenin (an extract from a Compositae Inula helenium L.). alantolactone and isoalantolactone (two isomeric sesquiterpene lactones), were assessed by sensitizing guinea pigs of different strains; albino Himalayan spotted. Pirbright and Hartley. Both alantolactone and isoalantolactone are found to be sensitizers if injected intradermally. Only Pirbright guinea pigs showed a high sensitization rate by the open epicutaneous technique; with this method, alantolactone was the more potent sensitizer. [ABSTRACT FROM AUTHOR]

Patients sensitive to phenyl salicylate (salol) were patch-tested to several aryl salicylates. The most powerful derivative was p-nitrophenyl salicylate (compound 5). This can be explained by an unusually good interaction with protein (nucleophilic substitution on the carboxyl carbon). All these results were confirmed by experimental sensitization of guinea pigs to salol and cross-reaction to substituted salols. The results are in line with current theory of allergic contact dermatitis, i.e., an in vivo formation of a hapten-protein conjugate. [ABSTRACT FROM AUTHOR]

Cross-sensitization between two plant allergens, Frullania and Laurus Nobilis (L), has been demonstrated in Strasbourg. A review of the haptens isolated from Frullania outlines the importance of the purification of allergen to ascertain the nature of the Causative agent. New results on laurel oil point to the possibility of a common denominator (the α-methylene γ-butyrolactone moiety) between this plant and Frullania; former results are re-interpreted and analyzed. In conclusion, the importance of physico-chemical methods used to purify and isolate haptens, and help in their definition, is stressed. [ABSTRACT FROM AUTHOR]

Cross-reaction in allergic contact dermatitis (ACD) is a highly stereoselective process. The importance of the cis or trans ring junction in α-methylene-γ-butyrolactones in cross-reactivity was investigated by reacting Helenin® (mostly a mixture of natural allergenic sesquiterpene lactones alantolactone &1bline; and isoalantolactone &2bline;, which present a cis ring junction) in guinea pigs sensitized to model allergenic &alpha-methylene-γ-butyrolactones; cis-bicyclic lactone 3 and trans-bicyclic lactone &4bline;. [ABSTRACT FROM AUTHOR]

Several compounds containing the α-methylene-γ-butyrolactone moiety have been tested on human volunteers and on guinea-pigs; the animals were experimentally sensitized by alantolactone, iso-alantolactone and laurel oil. Of the two new lactones, spirolactone was the more reactive: this was confirmed by both animal and human testing. The synthetic lactones are less reactive than natura1 ones. α-Methylene-γ-butyrolactone itself does not elicit cross-reactions in guinea-pigs sensitive either to alantolactone or to isoalantolactone, or in patients sensitive to sesquiterpene lactones. The α- methylene-γ-butyrolactone group is necessary for cross-reaction, but to be active, it has first to be substituted. It was also found that isoalantolactone, allegedly not allergenic, is in fact a sensitizer and cross-reacts with alantolactone. The cross-reaction between laurel and Frullania, found in man, also occurs in guinea-pigs. It is more evident when sesquiterpene lactone is the sensitizer and laurel used to elicit reaction. [ABSTRACT FROM AUTHOR]

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